1. Field of the Invention
This invention relates to medical instruments and more particularly to medical instruments for use in surgery to repair fractured bones.
2. Previous Art
Guide pins are used in certain selected orthopaedic procedures to correctly position a surgical implant so that anatomic reduction at the fracture is achieved. Examples of such fractures include simple supracondylar femur fractures; supracondylar fractures with associated comminution of the distal shaft; fractures of the lateral condyle extending up into the shaft; posterior tangential fractures of one or both condyles; inter- and supracondylar fractures (T or Y fracture); the bicondylar fractures combined with a comminuted fracture of the distal femur; and bicondylar fractures combined with distal comminuted fracture of the femoral shaft. Fractures at the proximal end of the femur, in the trochanteric and neck region, also require the use of guide pins.
In each of the surgical procedures to repair supracondylar femur fractures, intra-articular "primary" guide pins are used to align a "secondary" guide with respect to the knee joint and pin which in turn is used to correctly position the surgical implant across the fracture site.
The traditional surgical method for aligning and positioning the secondary guide pin is by a "free-hand" technique. Inherent in this "free-hand" technique is the risk of inaccurate placement of the surgical implant. This may result in a non-anatomic reduction of the fracture and an incongruous joint surface.
More specifically, the currently accepted procedure is to place two primary guide pins adjacent to the distal and anterior surfaces of the distal femur within the knee joint capsule A secondary guide pin is driven into the lateral surface of the distal femur parallel to the two primary guide pins. The selected implant is placed parallel to the secondary guide pin and should therefore be parallel to the distal and anterior articular surface of the distal femur. A detailed explanation of the above procedure is found in Manual of Internal Fixation Technique Recommended by the AO Group at 98-101, (Springer-Verlag Second Edition 1979) and Operative Orthopaedics Vol. 1, Ch33, "Supracondylar and Articular Fractures of the Distal Femur" at 401-412 (J.B. Lippincott Co. 1988) which are specifically incorporated herein by reference.
The accuracy of the placement of a secondary guide pin is based solely upon the perceptual skills of the operating surgeon and the one or two assistants who may be present. If the depth perception of either the surgeon or his assistants is inaccurate, the surgical implant will be placed inaccurately. This will produce a malreduction of the fracture and mal-alignment of the knee joint itself. A patient so afflicted may develop early degenerative arthritis and may lose substantial joint mobility. For some time, there has been a need for a guide system to replace the "free-hand" technique. The guide system should aide the surgeon and his assistants in precise placement of the selected implant with respect to the two inter-articular guide pins. Ideally, such a guide pin system would be used to simply and consistently orient a surgical implant parallel to the knee joint in three dimensions.